This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 63 |
| 3 | 231 |
| 4 | 3003 |
| 5 | 9009 |
| 6 | 51051 |
| 7 | 138567 |
| 8 | 2909907 |
| 9 | 7436429 |
| 10 | 37182145 |
| 11 | 91265265 |
| 12 | 882230895 |
| 13 | 2103781365 |
| 14 | 9917826435 |
| 15 | 23141595015 |
| 16 | 856239015555 |
| 17 | 1964313035685 |
| 18 | 8948537162565 |
| 19 | 20251952525805 |
| 20 | 182267572732245 |